This invention relates to an internal combustion engine having an integrally connected pressure-swing adsorption (PSA)system to provide oxygen-enriched air or oxygen-deficient air, in situ, to the mixing chamber of the engine.
The use of conventional internal combustion engines for use in the transportation of passengers and/or cargo has been part of our modern industrial society. The exhaust gas quality and fuel consumption efficiency are important features of the operation of internal combustion engine. These exhaust gas emission features have become increasingly more stringent and by-products of the exhaust gas could be harmful to the environment and human health. Ambient air supplied to the mixing chamber along with conventional fuel of an internal combustion engines produces nitrogen oxides, NOx, that are undesirable components of the exhaust emissions.
It has been understood for several years that the use of oxygen-enriched air in an internal combustion engine produces desirable operating results (i.e. increased power due to more complete fuel combustion and reduced emissions). This has become particularly important for large diesel-type engines such as those used in locomotives, but is also important for standard gasoline automobile engines since laws mandating lower pollutant emissions have been enacted.
U.S. Pat. No. 5,960,777 discloses a novel method of operating an internal combustion engine employing a selectively gas permeable membrane to provide either oxygen or nitrogen enriched air feed to beneficially affect engine performance. By feeding enriched air from a membrane unit such performance parameters as reduced NOx emissions, lean burn limit, engine power, and reduced cold start emissions can be enhanced relative to feeding ambient air. The selectively gas permeable membrane unit further includes a nonporous membrane (i) having an oxygen/nitrogen selectivity of at least 1.4 and a permeability to oxygen of at least 50 barrers; (ii) formed from an amorphous copolymer of perfluoro-2,2-dimethyl-1,3-dioxile; and (iii) being at a temperature below the glass transition temperature of the amorphous copolymer.
U.S. Pat. No. 5,678,526 discloses an internal combustion engine that has a system, including diagnostics, for providing oxygen enriched air so as to control emissions of unburned hydrocarbons and carbon monoxide. The system includes the capability of determining whether the oxygen enrichment system is providing suitable mass flow to the engine and whether oxygen enrichment is available according to the specifications of the enrichment device.
U.S. Pat. No. 5,649,517 discloses an air supply control system for selectively supplying ambient air, oxygen enriched air and nitrogen enriched air to an intake of an internal combustion engine includes an air mixing chamber that is in fluid communication with the air intake. At least a portion of the ambient air flowing to the mixing chamber is selectively diverted through a secondary path that includes a selectively permeable air separating membrane device due a differential pressure established across the air separating membrane. The permeable membrane device separates a portion of the nitrogen in the ambient air so that oxygen enriched air (permeate) and nitrogen enriched air (retentate) are produced. The oxygen enriched air and the nitrogen enriched air can be selectively supplied to the mixing chamber or expelled to atmosphere. Alternatively, a portion of the nitrogen enriched air can be supplied through another control valve to a monatomic-nitrogen plasma generator device so that atomic nitrogen produced from the nitrogen enriched air can be then injected into the exhaust of the engine. The oxygen enriched air or the nitrogen enriched air becomes mixed with the ambient air in the mixing chamber and then the mixed air is supplied to the intake of the engine. As a result, the air being supplied to the intake of the engine can be regulated with respect to the concentration of oxygen and/or nitrogen.
U.S. Pat. No. 4,351,302 discloses an apparatus for reduction of pollutant emissions by internal combustion engines that includes a tapered, coaxial multiconical structure used as a gas separator. The gas separator is used to provide oxygen enriched air to an engine, thus providing a reduction in the amount of nitrogen provided thereto. The resulting exhaust gas includes fewer oxides of nitrogen, reduced quantities of hydrocarbons, and decreased percentages of carbon monoxide. Air is directed through the structure, entering at a wide mouth throve. A fan may be provided for directing the air through the structure. The air exiting at the central portion of the narrow end of the structure, which has an increased ratio of oxygen to nitrogen, is directed by a conduit to the engine inlet. The structure is inexpensive, and easily mounted on existing engines, thus providing a retrofitting device for conforming older cars to current pollution standards.
U.S. Pat. No. 6,176,897 discloses a pressure swing adsorption separation of a feed gas mixture, to obtain a purified product gas of the less strongly adsorbed fraction of the feed gas mixture, and in a plurality of preferably an even number of adsorbent beds are used, with each adsorbent bed communicating at its product end directly to a variable volume expansion chamber, and at its feed end by directional valves to a feed compressor and an exhaust vacuum pump. For high frequency operation of the pressure swing adsorption cycle, a high surface area layered support is used for the adsorbent. The compressor and vacuum pump pistons may be integrated with the cycle, reciprocating at twice the cycle frequency.
Delivery of oxygen-enriched air to the intake of an internal combustion engine has been shown to reduce the emissions of air pollutants from the engine exhaust and increase the power output by driving the combustion of the fuel closer to completion. Some of the fundamental considerations of these phenomena were studies and presented in a technical paper by Lahiri, et al. (Lahiri, D. Mehta, P. S., Poola, R. B., and Sekar, R. R.; xe2x80x9cUtilization of Oxygen-Enriched Air in Diesel Engines: Fundamental Considerationsxe2x80x9d, International Combustion Engine, 1997 Fall Conference, Madison, Wis., September/October 1997). The computed properties, such as adiabatic flame temperature and exhaust gas composition as well as differences in thermodynamic and transport properties when oxygen-enriched air was used in place of normal atmospheric air in internal combustion engines were recited in this reference. The effects on parameters impacting engine performance such as fuel evaporation rate and ignition delay were also studied. This paper explains why oxygen-enriched air has beneficial effects when used in internal combustion engines.
A paper providing useful background information was presented by Ng and Sekar (Ng, M. K. and Sekar, R. R.; xe2x80x9cPotential Benefits of Oxygen-Enriched Intake air in a Vehicle Powered by a Spark-Ignition Enginexe2x80x9d, DOE Periodical 94013452, April 1994). Oxygen-enriched air (25%, 28%, and 30% by volume) was tested in a gasoline engine (3.1 L Chevy Lumina, 1990), and its effects on emissions were studies. The amounts of CO, hydrocarbons, and ozone were shown to decrease and the NOx was shown to increase at the outlets of the catalytic converter as well as the engine itself.
An objective of the present invention is to provide a means to generate oxygen-enriched or oxygen-deficient air, in situ, for apparatus in which the desired gas is produced from a pressure swing adsorption system that forms an integral part of the apparatus.
Another objective of the present invention is an internal combustion engine having a pressure swing adsorption system, as an integral part of the engine, to provide oxygen-enriched or oxygen-deficient gas for the mixing chamber of the engine.
Another objective of the present invention is a spark-ignition engine having a pressure swing adsorption system as an integral part of the engine and wherein the crank shaft and cam shaft of the engine also preforms the pressure and evacuation means for the pressure swing adsorption system.
Another objective of the present invention is a compression-ignition (diesel) engine having a separate pressure swing adsorption system assembled as an integral part of the engine.
With these and other objects in mind, the present invention is hereinafter described in several embodiments of the invention, and the novel features thereof being particularly pointed out in the appended claims.
The invention relates to an internal combustion engine having a pressure swing adsorption (PSA) system as an integral part of the engine comprising:
an internal combustion engine having a mixing chamber with an air inlet for the engine; and
at least one PSA bed containing an adsorbent material adapted for adsorbing oxygen or nitrogen from an ambient air and having a PSA bed air intake adapted for receiving ambient air and a PSA bed outlet adapted for discharging an oxygen-enriched air or an oxygen-deficient air product after the air is passed through the absorbent material, and said PSA bed outlet coupled to the inlet of the mixing chamber and operable such that the oxygen-enriched air or oxygen-deficient air from the integrally assembled pressure swing adsorption system of the engine can be fed into the mixing chamber for operating the engine. This internal combustion engine can have the adsorbent material selectively adsorb nitrogen so that an oxygen-enriched air can be fed into the mixing chamber of the engine intake or the adsorbent material can selectively adsorb oxygen so that an oxygen-deficient air can be fed into the mixing chamber of the engine intake.
Another embodiment of this invention relates to a spark-ignition internal combustion engine having an integrally assembled pressure swing adsorption (PSA bed) system wherein the engine contains an inlet, a crank shaft and a cam shaft; an intake of the PSA bed coupled to at least two cylinders having intakes and outlets with pistons operable in out of phase cycles for generating pressure differentials within the bed containing an adsorbent material for producing oxygen-enriched air or oxygen-deficient air for the engine inlet with said crank shaft and said cam shaft being coupled to and sequentially operating the pistons and cylinder intakes and outlets to produce oxygen-enriched or oxygen-deficient gas for the mixing chamber of the engine.
Another embodiment of this invention relates to a compression-ignition (diesel) internal combustion engine having a separate integrally assembled pressure swing adsorption system and wherein a turbo compressor of the engine has a turbo air inlet for receiving air and a turbo outlet coupled to an inlet of the PSA bed and operable such that the turbo compressor generates pressure differentials within the PSA bed containing an adsorbent material for producing oxygen-enriched air or oxygen-deficient air to be discharged from an outlet of the PSA bed and fed into a mixing chamber coupled to an inlet of the engine.
In summary, there are benefits for using oxygen-enriched air (or to a lesser degree, nitrogen-enriched air) as the oxidizer in internal combustion engines. There have been different methods proposed to supply the enriched air with the majority of the prior art utilizing semi-permeable membranes. The present invention proposes the use of a small PSA, preferably incorporated into the engine block as an integral part of the block, to supply desirable and selective air to the engine. One of the novel main features of the engine is the use of the drivers (i.e. crankshaft and cam shaft) to drive the PSA. Using the PSA as an integral part of the engine provides advantages in terms of energy usage and overall space requirements.
Prior art systems generally utilize semi-permeable membranes to enrich atmospheric air in oxygen or nitrogen for use in internal combustion engines. Ranges of concentration cited are from 23-40% by volume of oxygen (oxygen-enriched) and 80-98% by volume of nitrogen (nitrogen-enriched). The present invention uses a small PSA system requiring approximately 10 to 1000 lbs. of adsorbent material depending on engine displacement. Conventional automobiles should require about 25 lbs. to accomplish air enrichment and produce equivalent or superior results with regard to power output and emissions reduction using prior art membranes. Additionally, the PSA system is generally less sensitive than a membrane with regards to the presence of solid particles, and temperature fluctuations in the feed leading to a longer effective lifetime and less maintenance. There is also considerable flexibility in the quality of the oxygen that can be generated by the PSA so the unit can supply the optimum concentration of oxygen in air depending on the specific system requirement. The simplest apparatus can produce low to medium-grade oxygen between 22% and 30% oxygen, while other embodiments can produce high-quality oxygen above 80% of oxygen by volume.
Oxygen quality can be defined as follows:
Advantages of using the PSA as an integral part of the engine are that it provides efficient energy usage and overall minimal space requirements.
For spark- and compression-ignition systems using oxygen-enriched air, the adsorption material for the PSA bed can be zeolites containing one or more cations selected from the group comprising sodium, lithium, calcium, potassium, strontium ions and the like and preferably the adsorption material should be suitable for high temperature operations. For engines using oxygen-deficient air, the adsorption material for the PSA bed can be a porous framework comprising one or more transition element complexes (TECs) as disclosed in European application EP 1106245A.